256 PHYSIOLOGICAL CHEMISTRY 



tares of proteases and peptones. The former is mainly proteose, 

 the latter mainly peptone. 



1. Dissolve about a half teaspoonful of "Witte's peptone" in 

 sufficient water to cause solution. Boil to coagulate any un- 

 changed protein. Filter if necessary. Saturate the hot solution 

 with ammonium sulphate. Proteoses are precipitated. Remove 

 the precipitate either by filtering, or, if it has formed in clumps, 

 by collecting with a glass rod or with a small watch glass. If the 

 latter method has been employed, filter the liquid to remove any 

 remaining proteose, and reserve the filtrate for the study of pep- 

 tones in (b) below. Press the proteose 'precipitate between filter 

 papers to remove as much sulphate as possible, and dissolve in a 

 small amount of water. Add solid barium carbonate in excess 

 and boil. Filter from the preciptated barium sulphate and use 

 the filtrate which contains a mixture of proteoses, for the follow- 

 ing tests : 



(1) Biuret. Millon, Adamkiewicz. 



(2) Precipitation with concentrated HN0 3 . If a precipitate 

 forms, it consists of the so-called primary proteoses, the only 

 members of this group which are precipitated by nitric acid. 

 Performed as a "ring test," this test is known as Heller's ring 

 test. 



(3) Precipitate with picric acid. Warm and observe that the 

 precipitate dissolves. Cool. It reappears. 



(4) Note that proteoses are not coagulated by boiling, even in 

 acid solution. 



(5) The lower members of the proteose group are somewhat 

 diffusible through an animal membrane. 



(b) Peptones. The filtrate from proteoses reserved in (a) i. 

 which contains peptones, or preferably a solution of Armour's 

 peptone may be examined for peptones. After removal of pro- 

 teoses by saturating with ammonium sulphate, concentrate to a 

 small volume, cool, pour off the liquid from the ammonium sul- 

 phate crystals, and boil it with solid barium carbonate until sul- 

 phate is completely removed. Filter and test the filtrate for the 

 properties of peptones. 



